Cogito ergo sum: Latin for 'I
think therefore I am'. Briefly, the argument is also known as 'the
cogito', and is an argument for one's own existence. It is due to
Descartes, who believed it was certainly true.

Descartes
believed the cogito is an irrefutable and certain argument for one's own
existence. St Augustine, more than thousand years earlier, had a
somewhat better argument, involving a similar form and same principle: "Fallor
ergo sum" - if I am mistaken, then I still exist, even if I am
mistaken.

Both Descartes' and St. Augustine's do not really prove more than
that human beings can argue on the basis of definitions or meanings of
words, and that they easily can make mistakes while doing so, especially
because of wishful thinking.

This can be shown by several elementary arguments, all with the same
sort of logic as used by the arguments of Descartes
and
St. Augustine. Thus, one may consider "I dream, therefore I am"; "I
think I am an illusion, therefore I am an illusion"; "I am an illusion
of something unthinkable, therefore I am not"; or "I am a computer
program that cannot think but that can generate grammatical apparently
valid conclusions, therefore I am a thinking genius".

And in this context here is Ambrose Bierce for the edification of the
reader

"...Descartes, a famous
philosopher, author of the celebrated dictum, Cogito ergo sum -
whereby he was pleased to suppose he demonstrated the reality of human
existence. The dictum might be improved, however, thus: Cogito cogito
ergo cogito sum - 'I think that I think, therefore I think that I am';
as close an approach to certainty as any philosopher has yet made." (The
Enlarged Devil's Dictionary, entry
Cartesian)

As said, St. Augustine argued similarly, and did
so about 1200 years earlier. He argued, more plausibly "Fallor, ergo
sum" i.e. "I may be mistaken, so I am".

But in any case, such arguments do not
hold, however plausible they may seem to be. For if Descartes may be
misled by the devil in believing he sees a fair damsel where there is
none, there is no reason to believe that the devil may not make an
automaton - or some ape - that mistakenly believes itself to be the
philosopher Descartes, while being no such thing, and the same may be
replied to St. Augstine's more modest "If I am mistaken about what I
think, then at least I think": No, at best there is some appearance that
appears to say or think this: all that is logically valid in either
Descartes's or Augustine's arguments is to the effect that if there is
an experience of the so-and-so, there is an experience - but one may be
quite mistaken about what the experience is an experience of, for there
may be no so-and-so at all.

This is less fanciful or hardheaded
than the reader may believe (who might incline to "Come on! I know at
least that I exist, whatever you say, for whatever the explanation,
there are my feelings"), because, like a symphony, the sense of
self a
person has may be the product of many interacting contributors none of
which itself is or has a self. If so, the sense of self may still be
useful and important, or it may be a useless or even - as the Buddhists
and many mystics claim - a harmful illusion (not so much an optical
illusion as an illusion of the I), but at least in that case what we
hold to be our self is less of a unit than seems suggested by simple
pronouns.

Who wants to know more about the cogito, I refer to my
sections on Descartes
and Russell.
And whoever really desires certain knowledge, should seriously consider
logic and mathematics.